CATV services are normally provided by transmitting a plurality of television (TV) programs from a head end over television channels of a transmission line to a plurality of subscribers. The services provider normally supplies a set top box (STB) at each subscriber location for permitting reception of any of the desired channels by the television receiver of the subscriber. The set top box customarily comprises a tuner and a subscriber interface and display which permit the subscriber to designate desired TV channels by a mechanism that adjusts the tuner.
In addition, the provider may transmit from the head end a plurality of scrambled TV programs over a plurality of premium TV channels. Those subscribers which, for an added fee, are permitted to receive premium channels, have included in their set top boxes descramblers for permitting programs transmitted by the premium channel to be coherently received. In addition, pay-per-view (PPV) is a service sometimes provided to enable paying subscribers to watch a scheduled event at a particular time. This service may require, for example, that the subscriber communicate by telephone to the provider at the head end a request that he be permitted access to the scheduled event, whereupon the provider remotely actuates the descrambler at that subscriber's set top box permitting him to receive the scheduled event on a specified TV channel.
A service which is not currently available may be designated video on demand (VOD) service. With this service, a subscriber would communicate to the provider a request for a specified program, such as a videotaped movie, at a specified time. The provider would transmit the program or movie to the subscriber in a manner such that it could be received during the specified time only by the single subscriber requesting and paying for it, without reception by others. One way of providing such service would be to dedicate a plurality of premium channels for VOD service, and then to notify the subscriber which particular VOD channel he should select in order to receive the requested program. The provider would also activate the descrambler at the subscriber's set top box to permit reception of the transmitted movie. A disadvantage of this system is that, if there were many subscribers and many dedicated channels, it would require that the subscriber be advised which of many channels he should select at the desired time to receive the requested TV program. Another possible system for providing VOD service would include a switching system between the head end and the subscribers for switching an appropriate channel carrying a requested program at a proper time to the appropriate subscriber. This would be disadvantageous because it would require a significant capital expenditure.
Thus, there is a long-felt need in the industry for a method for providing video on demand services to subscribers in a way that is simple and easy for the subscriber to use and which is relatively inexpensive to provide.